Low breeding success of the Adelie penguin at Bechervaise Island in the 1998/99 season

This paper describes the diet and foraging behaviour of Adelie penguins (Py goscelis adeliae) at Bechervaise Island during 1998/99, a season of low bre eding success. Fifty-six percent of nests with eggs failed during the three weeks following first hatch. A breeding success of 0.43 chicks creched per nest was achieved, compared to previous seasons with higher annual breedin g success rates ranging from 0.69 to 1.06 chicks creched per nest. Evidence from analyses of foraging location, foraging trip duration and diet sugges ts that the death of chicks during the guard stage was due to an inadequate rate of food supply. In most previous seasons adults have foraged both at the continental shelf edge (particularly females) and locally (particularly males). This season male penguins carried out fewer local trips and both s exes spent longer at sea than in years of higher breeding success. Meal mas ses brought back to the chicks were within the normal range but extended fo raging trip durations reduced feeding frequency. These findings contrast wi th observations made in 1994/95 (a season in which all chicks died of starv ation), when smaller meals were delivered and birds foraged further offshor e than in this or any other season studied. The significance to CCAMLR of t hese variations in foraging behaviour is discussed.